Laser apparatus for treatment of a cataractous lens
Inventors
Kraemer, Darren • Cowan, Michael
Assignees
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Publication Number
US-10881551-B2
Publication Date
2021-01-05
Expiration Date
Abstract
An apparatus for microdisruption of cataracts in lens tissue by impulsive heat deposition comprising: a source of pulsed laser radiation, a user input device, a control circuit, and an optical waveguide configured to transmit the pulsed laser radiation. The light intensity which exits the optical waveguide has a wavelength selected to match an absorption peak of at least one component of the lens tissue, a pulse duration time shorter than a time required for thermal diffusion out of the laser irradiation volume and shorter than a time required for a thermally driven expansion of the laser irradiated volume, and a pulse energy resulting in a peak intensity of each laser pulse below a threshold for ionization-driven ablation to occur.
Core Innovation
The invention relates to an apparatus for disruption of cataracts in lens tissue enclosed by aqueous humour and/or vitreous humour. The apparatus delivers pulsed laser radiation to cataracts in the lens tissue through an optical waveguide configured to transmit the pulsed laser radiation from a source to a distal end within the eye.
A central aspect of the invention is control of the pulsed laser radiation to exhibit conditions at the distal end of the optical waveguide such that the exiting light intensity is sufficient to produce microdisruption of the lens tissue by impulsive heat deposition. The conditions include a wavelength in the range of about 2700 nm to about 3300 nm, selected to match an absorption peak of at least one component of the lens tissue.
The invention further specifies pulse duration time and energy-related constraints to manage tissue effects and collateral damage. The pulse duration time is selected in a range of about 10 ps to about 1 ns, or about 100 ps to about 1 ns in another independent claim, such that each pulse duration time is shorter than a time required for thermal diffusion out of the irradiated volume and shorter than a time required for thermally driven expansion to avoid shock wave propagation, while the selected pulse energy keeps peak intensity below a threshold for ionization-driven ablation and leaves residual energy insufficient to substantially damage material surrounding the irradiated volume.
Claims Coverage
The document includes two independent claims. Both independent claims cover an apparatus that disrupts cataracts by delivering pulsed laser radiation through an optical waveguide or optical fiber under parameter constraints that promote impulsive heat deposition microdisruption while limiting shock propagation, ionization-driven ablation, and collateral damage; each independent claim articulates multiple inventive condition constraints, particularly wavelength selection, pulse duration relative to thermal diffusion and expansion times, and energy or peak intensity limits tied to ionization-driven ablation and surrounding tissue damage.
Lens-tissue microdisruption by impulsive heat deposition with mid-IR wavelength match
An apparatus in which pulsed laser radiation is controlled to exhibit conditions at the distal end of the optical waveguide such that the light intensity exiting the optical waveguide is sufficient to produce microdisruption of the lens tissue by impulsive heat deposition, including a wavelength in the range of about 2700 nm to about 3300 nm selected to match an absorption peak of at least one component of the lens tissue, wherein the wavelength causes pulses to produce superheated temperatures above a vaporization point when absorbed in an irradiated volume.
Pulse duration shorter than thermal diffusion and thermally driven expansion to avoid shock propagation
In the apparatus, a pulse duration time in a range of about 10 ps to about 1 ns, or about 100 ps to about 1 ns, is selected such that each pulse duration time is shorter than a time required for thermal diffusion out of the laser irradiated volume and shorter than a time required for a thermally driven expansion of the laser irradiated volume to avoid shock wave propagation in the lens tissue.
Energy and intensity constrained below ionization-driven ablation threshold
In the apparatus, the combination of selected pulse duration time and selected pulse energy is low enough to result in a peak intensity of each laser pulse below a threshold for ionization-driven ablation to occur in the irradiated material.
Majority energy conversion to ablation with insufficient residual to substantially damage surrounding material
In the apparatus, the conditions are selected to result in conversion of a majority of the energy contained in each laser pulse to ablation of the material in the volume, with any residual energy being insufficient to substantially damage material surrounding the volume irradiated by the pulsed laser.
Optical fiber delivery with defined distal end geometry
An apparatus in which the optical waveguide is an optical fiber with a curved, tapered, or conical distal end, the optical fiber coupleable to the source at a proximal end to receive the pulsed laser radiation from the source.
Across both independent claims, the coverage centers on a cataract-disruption apparatus using controllable pulsed laser radiation delivered via an optical waveguide or optical fiber to the eye, with wavelength matched to an absorption peak of lens tissue and with pulse duration and energy or peak intensity constraints designed to promote impulsive heat deposition microdisruption via vaporization-related superheating while avoiding shock wave propagation and keeping peak intensity below an ionization-driven ablation threshold. Both claims further require that most of each pulse’s energy converts to ablation of the targeted volume with residual energy insufficient to substantially damage surrounding material.
Stated Advantages
Converting a majority of the energy contained in each laser pulse to ablation of the irradiated volume while any residual energy is insufficient to substantially damage surrounding material.
Avoiding shock wave propagation in the lens tissue by selecting pulse duration time shorter than thermal diffusion and thermally driven expansion times.
Reducing the occurrence of ionization-driven ablation by maintaining peak intensity below a threshold for ionization-driven ablation.
Producing microdisruption of the lens tissue by impulsive heat deposition.
Documented Applications
Disruption of cataracts in lens tissue enclosed by aqueous humour and/or vitreous humour.
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